Comment by jandrewrogers

There is a large variance in AVX-512 performance across the microarchitectures, particularly the early ones. In addition to throttling, which was mitigated relatively early, some relatively feature-complete microarchitectures (e.g. Ice Lake) were sensitive to alignment. The microarchitectures with these issues are approaching obsolescence at this point. AVX-512 runs very well with predictable performance on most vaguely recent microarchitectures.

In my case I find AVX-512 to be usable in practice because the kinds of users that are obsessed with performance-engineered systems are typically not running creaky hardware.